Transformer



Z- 31, 1937- H. A. w. KLINKHAMER 2,091,366

TRANSFORMER Filed May 25, 1936 Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE TRANSFORMER Gloeilampenfabrieken, lands Eindhoven, Nether- Application May 25, 1936, Serial No. 81,722 In Germany June 25, 1935 8Claims.

My invention relates to variable-leaka e transformers.

It is well known to control the leakage and consequently the secondary current of a transformer by providing adjustable iron bridgepieces or shunts between its secondary and primary windings. However, such transformers, because of their construction, have several drawbacks which prevent their use for various puro poses. In case the transformer is of the core type a fairly strong external field exists, which may induce eddy currents in surrounding iron objects,

which results in power losses. Furthermore, in both the coreand shell-type transformers such adjustable shunts always produce more or less pronounced humming unless comparatively complicated and expensive means are provided for guiding and holding the shunts.

' In addition, due to-the magnetic forces, the adjusting mechanism for the shunts is liable to become jammed and distorted, and also variations in the air gap may occur which change the adjusted value of the short-circuit reactions for a given position of the shunts. To eliminate these dimculties, the adjusting mechanism must be quite heavily constructed, which increases the cost as well as the sire and weight of the transformer.

The object of my invention is to overcome the above difllculties and to provide a variable leakage transformer of small size and of very simple and inexpensive construction.

According to my invention, I use a shell-type transformer and slidably dispose the adjustable bridge-pieces within the space formed between its windings, and provide means to shift the bridgepieces relative to each other, whereby they are pressed against either the central leg or the yokes of the core.

My invention has particular advantages when used with a plurality of transformer units, for instance with two single-phase units serving to transform three-phase current into four-phase current, which is to be rectified into D. C. welding current. In such cases the clamping means can be made very simple by arranging the transformer units with their laminations in parallel planes and with the respective bridge-pieces in alignment, whereby the corresponding bridgepieces of the transformer units are mechanically interconnected and the adjustment of all the bridge-pieces takes place simultaneously.

I am aware that it is known to use shell-type transformers having adjustable shunts for feeding luminous tubes in which a high leakage is desirable. However, in such cases there is no necessity for adjusting the shunts after the transformer -has been placed into service and therefore an admust be frequently adjusted during the operation of the transformer, then the provision of the two shunts entails considerable difllculty. Although it is possible to mechanically interconnect the shunts to form a unit, this does not eliminate the 10 difhculties.

In order that my invention may be clearly understood and readily arried into effect, I shall describe same more fully with reference to the accompanying drawing, in which:

Figure l is a sectionized elevation of a shelltype transformer according to the invention;

Fig. 2 is a sectionized view taken along line 2-2 ofFigure 1;

Fig. 3 is a sectionized view taken along line 3-3 of Fig. 2;

Fig. 4 is a partly sectionized view of two transformer units of the type, shown in Figs. 1 to 3 as used for transfonning three-phase current into four-phase current.

Fig. 5 is a sectionized side view of Fig. 4.

4 The shell-type transformer shown in Figures 1 to 3 has a laminated core having a central leg 40, and two outer legs or yokes 2 and 3. Surrounding the central leg 40 is a primary winding and a secondary winding 3 l. Within the space between the coils 30 and 3| and movable ina direction perpendicular to the plane of the drawing are two bridge-pieces or magnetic shunts I and 5 having laminations extending normally to the axis of the central leg 40. The bridge-pieces 4 and 5 are secured, for instance by rivets, between strips 6 and 1 and strips I and 9 respectively of non-magnetic material, for instance brass. Instead of using two strips for each bridge-piece, a single strip clamped centrally between the laminations may be provided (see Figs. 4 and 5).

As shown in Figs. 2 and 3, the strips 6 to 9 extend beyond the transformer core, and the bridge-pieces 4 and 5 are movable in the direction of the arrow 32 to vary the leakage of the transformer and thus control the secondary current. The movement of the bridge-pieces l and 5 may be efiected by directly moving the pieces manually, or mechanical adjusting means may be provided for this purpose. As shown in Fig. 2, a bar 33 is rigidly secured at one end to the strip I and is provided on its free end with a threaded borevcooperating with the threaded end of an adlusting shaft 34, rotatably but not slidably mounted in a member and provided on its end with an operating wheel 36. The member 35, forms part of the transformer housing 45 in which the transformer is fastened by means of angle irons 4B49. For this purpose, various other constructions, for instance a rack and pinion, may be used.

To rigidly secure the bridge-pieces in any adjusted position, clamping means are provided whereby the bridge-pieces are forced against the core. For this purpose bolts l0 and II provided with wing nuts I6 and IT respectively extend between the strips of the bridge-pieces and clamp same together through cross pieces |2, l3, l4, and 5. Thus, when the bridge-pieces are adjusted to the desired position, the wing nuts are turned to force the bridge-pieces against the central leg, thereby preventing vibration and humming of the bridge-pieces as well as of the parts of the clamping device.' Instead of clamping the bridge-pieces together against the leg 6, they may be forced apart so as to press against the yokes 2 and 3. For this purpose the bolts Hi and I I are replaced by suitable means for forcing the strips apart.

To prevent the core laminations from shortcircuiting the strips 6-4 and 8-9, as well as the laminations of the bridge-pieces, bushings 31 of insulating material are provided. Furthermore, to prevent the bolts l0 and H, cross-pieces l2 to |5, and strips 6 to 9 from acting as a shortcircuited winding, insulating material must be provided at suitable points. For instance, the cross pieces l2 and I3 or strips Id and I5 may be of insulating material, or either the strips 6 and 8 or the strips 1 and 9 may be of insulating material.

As shown in Figs. 4 and 5, two single-phase shell-type transformer units A and B of a construction similar to that shown in Figs. 1 to 3, are combined to form a transformer device, for instance for supplying four-phase current to a rectifying device from a three-phase source. The

, invention is particularly adapted for use in connection'with such transformers, as the clamping and simultaneous adjustment of the bridge-pieces can be effected in a very simple manner. In such a device the transformer units are arranged with their laminations parallel and with the bridgepieces in alignment. The'correspondin'g bridgepieces' of the transformer units are interconnected by means of strips 2| and 22 clamped between the laminations of the bridge-pieces (see Fig. 5), whereas only a single clamping device 23 is used to clamp all the bridge-pieces against the central leg of the transformer 'core.

The clamping device 23 consists of two strips 3'! extending one on each side of the strips 2| and 22 and secured together at their ends by blocks 25 and 38. The block 25 is provided with a threaded bore which cooperates with'a threaded shaft 26 carrying'on its end an adjusting wheel 24. The free end of shaft 26 is provided with a plate 39 bearing against the strip 22. Upon rotation of wheel 24, the strips 2| and 22 are moved together whereby the bridge-pieces are pressed against the central legs of the cores. Instead of moving the strips 2| and 22 together, they may be moved apart so that the bridgepieces are pressed against the outer legs or yokes.

For adjusting the amount of leakage, the strips 2| and 22 are moved together in the direction of the arrow 43,- for instance by an adjusting mechanism of the type shown in Fig. 2.

While ,I have described my invention in con- .nection with specific examples and applications,

I do not wish to be limited thereto but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:-

1. A shell-type variable-leakage transformer comprising a core having a central leg and two yokes, windings spaced apart upon said central leg, two bridge-pieces of magnetic material disposed between'said windings, said bridge-pieces being disposed one between each yoke and the central leg and being movable therebetween to vary the leakage of the transformer, and means interconnecting said bridge-pieces for shifting same relative to each other to clamp same against the core.

2. A shell-type variable-leakage transformer comprising a laminated core having a central leg and two yokes, windings spaced apart upon said central leg, two bridge-pieces of magnetic material between said windings and each disposed between said central leg and one of said yokes, said bridge-pieces being movable between said central leg and yokes in a direction perpendicular to the plane of the core laminations to vary the leakage of the transformer, and means interconnecting said bridge-pieces for shifting same relative to each other to press same against the core.

3. A shell-type variable-leakage transformer comprising a laminated core having a central leg and two yokes, windings spaced apart upon said central leg, two bridge-pieces of magnetic material disposed between said windings and one between said central leg and each yoke and movable therebe'tween, means to simultaneously move said bridge-pieces in a direction normal to the plane of the core laminations to vary the leakage of the transformer, and means interconnecting said bridge-pieces for moving same together to clamp sam'e against the central leg.

4. A shell-type variable-leakage transformer comprising a. laminated core having a central leg and two yokes, windings spaced apart upon said central leg, two bridge-pieces comprising laminations of magnetic material, said bridgepieces being disposed between said windings one between said central leg and each yoke with the laminations extending normally to the axis of the central leg, means to move said bridge-pieces perpendicularly to the core laminationsto vary the leakage of the transformer, and means interconnecting the bridge-pieces for shifting same relative to each other to clamp same against the core. I

5. YA shell-type variable-leakage transformer comprising a laminated core having a central leg and two yokes, windings spaced apart upon said v said plates to move same relatively to each other and to clamp same against the core.

' 6. A transformer device comprising a plurality of shell-type variable-leakage transformers, each of said transformers'comprising a laminated core having a; central leg and two yokes,

nd extending beyond the windings spaced apart upon said central leg, two magnetic shunts eaich disposed between said windings and movable between said central leg and one of said y'okes to vary the leakage of the transformer, said transformers being arranged with their laminations parallel and with their shunts in alignment, members mechanically interconnecting the aligned shunts, means for simultaneously adjusting the positions of all the bridge-pieces, and a single clamping device interconnecting said members to move the shunts" relative to each other and clamp same against the cores of the transformers. A

7. A transformer device comprising two shelltype variable-leakage transformers, each of said transformers comprising a laminated core having a central leg and two yokes, windings spaced apart upon said central leg, two bridge-pieces of magnetic material each disposed between said windings and movable between said central leg and one of said yokes to vary the leakage of the transformers, said transformers being arranged with their laminations parallel and with the bridge-pieces in alignment, means including members mechanically interconnecting the aligned bridge-pieces for simultaneously adjusting the pomtion of the bridge-pieces, and a clamping device interconnecting said members at a point between the transformers for moving the bridge-pieces to clamp same against the core.

8. A transformer device for transforming three-phase current into four-phase current comprising two shell-type variable-leakagetransformers, each of said transformers comprising a core having a central leg and two yokes, windings spaced apart on said central leg, two bridgepieces of magnetic material eaichv disposed between said windings and movable between said central leg and one of said votes to vary the leakage of the transformer, said transformers being arranged with their laminaiions parallel and with the bridge-pieces in-t, means to simultaneously adjust the positions of said bridge-pieces, and means including a single clamping device for moving said bridge-pieces relative to each other to clamp sameagainst said core.

, WIJNAND 

